If you're interested in having an incredibly accurate clock in your home or workplace, it's possible to make your own with an Arduino or compatible board that can retrieve the correct time from a network time server over the Internet using the Network Time Protocol. Doing so is quite simple, with only an Ethernet-enabled Arduino and a display of some sort to keep you updated.

A neat example of an NTP clock has been demonstrated by Instructables member kariaa who uses the inexpensive ESP8266-based serial module as a bridge between the Arduino-compatible board and the Internet's time servers. The code is quite simple and gives you the framework for all sorts of accurate time pieces, such as the example below: